Solve for $x$ and $y$ using substitution. ${5x+2y = -7}$ ${y = 2x+1}$
Since $y$ has already been solved for, substitute $2x+1$ for $y$ in the first equation. ${5x + 2}{(2x+1)}{= -7}$ Simplify and solve for $x$ $5x+4x + 2 = -7$ $9x+2 = -7$ $9x+2{-2} = -7{-2}$ $9x = -9$ $\dfrac{9x}{{9}} = \dfrac{-9}{{9}}$ ${x = -1}$ Now that you know ${x = -1}$ , plug it back into $\thinspace {y = 2x+1}\thinspace$ to find $y$ ${y = 2}{(-1)}{ + 1}$ $y = -2 + 1$ $y = -1$ You can also plug ${x = -1}$ into $\thinspace {5x+2y = -7}\thinspace$ and get the same answer for $y$ : ${5}{(-1)}{ + 2y = -7}$ ${y = -1}$